This enigmatic monster originates from one of the moons of Ymgarl, but has spread throughout space and is threatening to become a real menace. In its native state it is blue, has two pairs of clawed arms, a long muscular tail and a tough leech-like body. Its head is a simple tube of slobbering tendrils and sharp inward-pointing teeth. What makes the Genestealer truly unique is its deadly and extremaly rapid reproductive cycle. Genestealers are of a single gender, and are incapable of reproducing amongst themselves. To reproduce they require another creature, any creature will suffice, of any gender. For all the Genestealer requires is the basic genetic material which is contained in every living cell of the mate. A Genestealer implants its own genetic material in the form of an egg capsule, which is forced into the body of the host by an estendible ovipository normally secreted inside the head. The implantation does not kill the mate immediatelly, but the implanted egg quickly grows until ready to burst out as an immature Genestealer. Needless to say, this kills the parent/host. Interestingly enough, newly born creatures, although fundamentally Genestealers, will have characteristics inherited from the host parent. Thus a Genestealer/human may have a vaguely humanoid head, or only two arms instead of the usual four, and perhaps its tail will be shortened and missing. A Genestealer of four or more generations consistent human parentage would pass for a human on cursory inspection, although a closer look would reveal a bluish skin, sharp pointed teeth and rather disturbing stare. On their home world, Genestealers exploit a large leech-like creature called a Csith, which is the usual mate. Matings with a Csith always produce natural Genestealers, no matter what its parentage otherwise.